Feasibility study on recycling of grass carp feces by Pomacea canaliculate

In order to study whether apple snail (Pomacea canaliculate) can utilize the feces produced by grass carp (Ctenopharyngodon idellus) effectively after being fed with water hyacinth (Eichhornia crassipes), we analyzed the growth index, body composition, digestive enzyme activity and accumulation of nitrogen and phosphorus in grass carp feces group and water hyacinth bait group, respectively. The results show that: 1) The body mass in the two groups increased very significantly after 35 d (P<0.01). Both the specific growth rate (SGR) and food conversion rate (FCR) in water hyacinth group were very significantly higher than those in feces group (P<0.01). There was no significant difference in the survival rate (SR) between the two groups (P>0.05). 2) The difference in body composition between the two groups of snails was not significant (P>0.05). 3) The activity of gastric amylase in water hyacinth group was significantly higher than that in feces group (P<0.05), and there was no significant difference in cellulase and lipase activity between the two groups (P>0.05). 4) Apple snail accumulated nitrogen and phosphorus elements in both groups without significant difference (P>0.05). In summary, the feces of grass carp can meet the basic growth requirements of apple snails and reduce the nitrogen and phosphorus contents in water indirectly. It is suggested that apple snails can be used to reduce the pollution brought by grass carp feces in "water-water hyacinth-grass carp" farming mode.